Method for measuring sandability of coating and the use thereof

ABSTRACT

The present invention is directed to a method for measuring sandability of a coating or an article. This invention is particularly directed to a method for measuring sandability of a coating or an article quantitatively by measuring weight loss of said coating or article after being sanded. This invention is also directed to a system for measuring sandability of a coating or an article using said method.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.12/663,918, filed Dec. 10, 2009, now U.S. Pat. No. 8,434,377, which is aU.S. National-Stage entry under 35 U.S.C. §371 based on InternationalApplication No. PCT/US08/68693, filed Jun. 30, 2008, which was publishedunder PCT Article 21(2) and which claims priority to U.S. ProvisionalApplication No. 60/937,821, filed Jun. 29, 2007, which are all herebyincorporated in their entirety by reference.

FIELD OF INVENTION

The present invention is directed to a method for measuring sandabilityof a coating or an article. This invention is particularly directed to amethod for measuring sandability of a coating or an articlequantitatively. This invention is also directed to a system that usessaid method to measure sandability of a coating or an article.

BACKGROUND OF INVENTION

It is a normal practice that after a coating composition is applied to asubstrate to form a coating, the coating is then sanded to removedefects to create a desired coating surface. The desired coating surfacecan have desired smoothness or roughness that may be different from theoriginal coating. Another layer or multiple layers of the same ordifferent coating composition can be applied over the sanded coatingsurface to finish the substrate.

Different coating compositions can have different intrinsic propertiesthat cause resulted coatings to have different sandability. Sandabilityof a coating describes how easy to sand the coating and is currentlyevaluated by specialists in the coating industry by sanding the coatingwith hand or tools. The specialists then ranking the coating orcoatings, based on their judgment, as easy or difficult to sand. Theevaluation is mostly subjective and varies from person to person. Sinceeach specialist may use different tools or sanding papers for performingsanding, the evaluation is often not reproducible and inconsistent.Current, there lacks a quantitative measure for evaluating sandabilityof a coating.

It is therefore in need for a method for measuring sandability of acoating efficiently, quantitatively and reproducibly.

STATEMENT OF INVENTION

This invention is directed to a method for measuring sandability of acoating, said method comprising the steps of:

-   -   a) measuring initial characteristics of a substrate coated with        said coating;    -   b) sanding said coating on the substrate;    -   c) measuring subsequent characteristics of the substrate after        the step b); and    -   d) obtaining a difference between the initial and the subsequent        characteristics.

This invention is directed to a method for measuring buffability of acoating comprising the steps of:

-   -   e) measuring initial surface characteristics of the coating        using a surface measuring device    -   f) buffing the coating to create a buffed coating surface; and    -   g) measuring subsequent surface characteristics of the buffed        coating surface using the surface measuring device.

This invention is further directed to a method for comparing sandabilityof a plurality of coatings, said method comprising the steps of:

-   -   a) measuring individual initial characteristics of individual        substrates each coated with one of said plurality of coatings;    -   b) sanding the coating on each of the individual substrates;    -   c) measuring subsequent characteristics of each of the        individual substrates after the step c); and    -   d) obtaining individual differences between the individual        initial and the corresponding subsequent characteristics.

This invention is further directed to a method for comparing buffabilityof a plurality of coatings comprising the steps of:

-   -   e) measuring initial surface characteristics of each of the        coatings using a surface measuring device;    -   f) buffing each of the coatings to create individual buffed        coating surfaces; and    -   g) measuring a subsequent surface characteristics of the buffed        coating surfaces using the surface measuring device.

This invention is further directed to a system for measuring sandabilityof a coating, said system comprising:

-   -   a) a sanding device; and    -   b) an substrate measuring device.

This invention is even further directed to a method for measuringsandability of an article, said method comprising the steps of:

-   -   a) measuring initial characteristics of the article;    -   b) sanding the article;    -   c) measuring subsequent characteristics of the article after the        step b); and    -   d) obtaining a difference between the initial and the subsequent        characteristics.

This invention is even further directed to a method for measuringbuffability of an article comprising the steps of:

-   -   e) measuring initial surface characteristics of the article        using a surface measuring device;    -   f) buffing the article create a buffed surface; and    -   g) measuring subsequent surface characteristics of the buffed        coating surfaces using the surface measuring device.

BRIEF DESCRIPTION OF DRAWING

FIGS. 1A, 1B, and 1C are flow charts of methods for measuringsandability and buffability in accordance with exemplary embodiments.

FIGS. 2A-2D show a representative example of a sanding device where:

FIG. 2A is a side view of the sanding device in accordance with anexemplary embodiment;

FIG. 2B is a photograph of an example of the sanding device of FIG. 2A;

FIG. 2C is a perspective side view of part of the sanding device of FIG.2A for illustrating movement control; and

FIG. 2D is a top-down view of part of the sanding device of FIG. 2A forillustrating movement control;

FIGS. 3A and 3B show a representative example of a buffing device where:

FIG. 3A is a side view of the buffing device in accordance with anexemplary embodiment; and

FIG. 3B is a photograph of an example of the buffing device of FIG. 3A.

FIG. 4 is a graph of quantitative sanding results using the method ofthis invention; and

FIGS. 5A-5C show representative sanding and buffing results, where:

FIG. 5A shows profilometer measurements after sanding but beforebuffing;

FIG. 5B shows profilometer measurements after sanding and 6 seconds ofbuffing; and

FIG. 5C shows profilometer measurements after sanding and 48 seconds ofbuffing.

DETAILED DESCRIPTION

The features and advantages of the present invention will be morereadily understood, by those of ordinary skill in the art, from readingthe following detailed description. It is to be appreciated that certainfeatures of the invention, which are, for clarity, described above andbelow in the context of separate embodiments, may also be provided incombination in a single embodiment. Conversely, various features of theinvention that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any sub-combination.In addition, references in the singular may also include the plural (forexample, “a” and “an” may refer to one, or one or more) unless thecontext specifically states otherwise.

The use of numerical values in the various ranges specified in thisapplication, unless expressly indicated otherwise, are stated asapproximations as though the minimum and maximum values within thestated ranges were both proceeded by the word “about.” In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as values within the ranges.Also, the disclosure of these ranges is intended as a continuous rangeincluding every value between the minimum and maximum values.

As used herein:

A coating means a thin layer of material covering a surface of asubstrate, such as metal, wood, plastic or any other articles ormaterials that a coating can be applied onto. Examples of substrateinclude, but not limited to, automobile body, metal panels, plasticpanels, wood panels, buildings, household appliances, sports equipments,or farming machines The coating can be formed by applying a thin layerof a coating composition to said substrate. A coating compositiontypically comprises materials that can form a thin layer under certainconditions. Examples of coating compositions include, but not limitedto, acrylic coating composition that comprises acrylic materials, latexcoating composition that comprises latex materials, and other coatingcompositions that comprises natural or manmade materials. A coatingcomposition can further comprise pigments or dyes to produce color. Acoating composition can also comprise special effect pigments such asaluminum flakes to produce special appearance effects such as sparkling.A coating composition is typically applied to a substrate by spraying,brushing, submerging or immersing, doping, or any other methods that cancause the coating composition to cover the substrate to form a coatedsubstrate.

A coating can be a single layer formed by a single coating composition.A coating can also have multiple layers formed by one or more coatingcompositions. In one example, a coating is a single layer formed by acoating composition applied directly to a substrate. In another example,a coating on a substrate comprises one or more primer layers formed byone or more primer compositions, one or more basecoat layers formed byone or more basecoat compositions, and one or more topcoat layers formedby one or more topcoat compositions.

A primer refers to a coating that can be applied to a substrate to forma primer layer to prepare the substrate so additional coating layers canbe applied. A primer can comprise adhesion promoter for improvedadhesion between the primer layer and the substrate. A primer can alsocomprise one or more pigments to produce desired color. A primer canfurther comprise anti-corrosion additives for protecting the substrate.A primer can also be referred to as a sealer or a surfacer that can beused to seal small defects on the surface of a substrate.

A basecoat refers to a coating applied over a primer layer or directlyover a substrate. A basecoat can be pigmented to produce desired coloror un-pigmented. One or more layers of basecoat can be formed by one ormore basecoat compositions.

A topcoat refers to a coating applied over a basecoat layer. A topcoatgenerally provides protection for a basecoat. A topcoat can be pigmentedor un-pigmented.

A clearcoat refers to a coating generally un-pigmented.

This invention is directed to a method for measuring sandability of acoating. In one embodiment, said method comprises the following steps.

In step a) (10) (FIG. 1), initial characteristics of a substrate coatedwith said coating is measured. The initial characteristics can bemeasured with a variety of ways. Examples of such initialcharacteristics include, but not limited to, initial weight of thesubstrate coated with the coating, initial thickness of the coating onthe substrate, and initial roughness or initial surface profile of thecoating on the substrate.

The initial weight of the substrate coated with the coating can bemeasured using a weight measuring device, such as a balance. It ispreferred that the balance is capable of measuring weight difference ina range of from about 0.0001 to about 1 gram. Thickness of the coatingon the substrate can be measured using a thickness gauge. Commerciallyavailable thickness gauges. Such as thickness gauge micro-TRI-glossμfrom Byk-Gardner, Columbia, Md. 21046, is suitable for this invention.Roughness of the coating can be measured using a gloss meter, such asthe gloss meters available from above mentioned Byk-Gardner. A coatinggenerally reduces gloss after being sanded. Roughness can also bemeasured by using an imaging device. Images of the coating surface canbe captured by the imaging device and enlarged for manual or automatedanalysis. Microstructures of the coating surface, such as microscopiclines, dots, grooves, dents that contribute to coating roughness can beanalyzed and recorded. Images can be real-time image and can also bestored optically or digitally, such as stored in a photograph or incomputer readable digital forms. Imaging devices, such as a stillcamera, a digital camera, a video camera, a microscope, or a scanner aresuitable for this invention. The roughness can also be measured using aprofilometer. A profilometer can measure special depth or height ofmicrostructures of the coating surface. The measurement can be analyzedand recorded. Commercial profilometers, such as those available fromAmbios Technology Inc (Santa Cruz, Calif.), Veeco (Woodbury, N.Y.),Solarius Development Inc. (Sunnyvale, Calif.), Taylor-Hobson Inc (WestChicago, Ill.) and CSM Instruments Inc. (Needham, Mass.), are suitablefor this invention.

In step b) (11), the coating on the coated substrate is then sanded. Thesanding can be done according to conventionally well known methods, suchas using sand papers, sand blocks, or other sanding media such assanding paste. Any conventional sanding methods are suitable for thisinvention.

The coating can also be sanded under controlled sanding conditions,wherein under said controlled sanding conditions, a number of factorsthat affect sanding, such as directions of sanding, the number ofsanding strokes, forces applied to sanding (hereafter referred to assanding force), or types of sanding media such as sanding paper, areregulated and recorded. In one example, a pre-determined number ofstrokes, such as 8 strokes, can be used to sand the coating in abi-directional fashion, with a pre-determined sanding force applied.

FIG. 2 shows an example of a sanding device for sanding the coatingunder controlled sanding conditions. The sanding device comprises asanding head assembly (201), a substrate holder (202) and a movementcontrol device (203) that causes relative movement between the substrateholder and the sanding head assembly. The sanding head assembly can beattached to a frame (204) through a coupling (211). In an example, thesanding head assembly comprises an arm (210), a sanding force regulator(209), a sanding head (207), a coupling (208) that couples the arm (210)and the sanding head (207). A sanding medium (206) can be attached tosanding head (207). One example of the sanding medium is a sanding blockavailable from Canal Rubber Supply Co., INC (New York, N.Y.). Thesanding block can be affixed to the sanding head with double sideadhesive paper. Sanding papers such as Imperial Wetordry 400, 600, 800,1000, 1200, 1500 and 2000 from 3M (St. Paul, Minn.) can be used. Othercommercial abrasives can also be used.

The substrate (205) can be placed on the substrate holder (202) with acoated side that is coated with the coating facing the sanding head. Thesubstrate holder (202) can be magnified so it can hold a steel or ironsubstrate. The holder (202) can also comprise other means such as clips,clamps, or screws that can hold the substrate in place.

The movement control device (203) provides desired relative motionbetween the sanding head and the substrate. The desired relative motioncan be bi-directional, such as motions in X-X′ or Y-Y′ direction (FIG.2C and D), or circular. The motions can also be partial circularoscillation or in a pre-determined direction between the X-X′ and Y-Y′directions. The movement control device can optionally provide verticalmoment in the Z-Z′ direction. The movement control device can beassembled from commercial available parts and devices. In one examplethe movement control device can be assembled from a linear stage fromTechno-Isel (part# HL31SBM601050010) (New Hyde Park, N.Y.), a motioncontroller S13540 from Applied Motion Products Inc. (Groton, Mass.) anda turntable from Vue-More Manufacturing Group (Nutley, N.J.). Aphotograph of an example of such sanding device is shown in FIG. 2B. Inthis particular example, the movement control device is placed under thesubstrate holder. The movement control device can also be place in otherlocations as long as it can cause relative motion between the sandinghead and the substrate. For example, the movement control device can beplaced in conjunction with the coupling (211) to cause the arm (210) tomove in X-X′ direction while the substrate holder remains stationary.The movement control device can also be placed on the arm (210) andcoupled to the sanding head to cause the sanding head to slide while thesubstrate holder remains stationary. Those skilled in the art canreadily make other configurations to establish relative movement betweenthe sanding head and the substrate holder to accomplish sanding of thecoating.

In step c) (12), subsequent characteristics of the substrate aftersanding can be measured. Sanding process removes certain amount ofcoating materials from the coated substrate causing the coating to loseweight and thickness. Sanding can also cause the coating to increaseroughness. Subsequent characteristics of the substrate can be measuredaccording to the initial characteristics measured. For example, if theinitial characteristics include weight, then the subsequentcharacteristics should also include weight. It is preferred that samedevice used for measuring the initial characteristics be used formeasuring the corresponding subsequent characteristics.

In step d) (13), a difference between the initial and the subsequentcharacteristics can be obtained. If weight of the substrate is used, aweight difference, also referred to as weight loss, between the initialweight and the subsequent weight can be obtained by subtracting thesubsequent weight from the initial weight. For example, if one coatedpanel has an initial weight of 100.00 gram and a subsequent weight of99.78 gram after sanding, then the weight loss due to sanding is about0.22 gram.

Thickness difference can be obtained based on initial thickness of thecoating on the substrate and subsequent thickness of the coating afterbeing sanded. A roughness difference can be obtained in a similar way.For example, a gloss difference can be obtained based on initial glossmeter readings before sanding and subsequent gloss meter reading aftersanding. Roughness difference can also be obtained by comparing imagesof the coating surface before and after sanding. Typically, numbers orsizes of the microstructures of the coating surface can be compared. Inone example, the numbers of lines and grooves per square millimeterappearing in initial and subsequent images of the coating are compared.Roughness difference can also be obtained by comparing profilometerprofiles. A sanded coating surface generally has increased roughnesssuch as increased depth or heights of the microstructures.

When necessary, the steps b) (11) through d) (13) can be repeated untildesired difference between the initial and the subsequentcharacteristics can be achieved. For example, the weight loss needs tobe exceeding a detection threshold of the balance used in order to bedetected. If a first set of sanding cannot remove sufficient coatingmaterials to cause a significant weight loss that can be detected by thebalance, the coating needs to be sanded again until the weight loss canbe detected by the balance. The difference between the initial and thesubsequent characteristics can be part of sandability data (14) forevaluating sandability of the coating, wherein the sandability data ofthe coating describe sandability of said coating.

How easy a coating can be sanded is often referred to as sandability ofthat coating. For coatings that are difficult to sand, repeated sandingmay be needed to remove significant amount of that coating so a weightloss can be obtained. Traditionally, sandability is evaluated byspecialists in the coating industry by sanding the coating with hand ortools. Based on their judgment, the specialists then ranking the coatingor coatings as easy or difficult to sand. The evaluation is mostlysubjective and varies from person to person. Since each specialist mayuse different tools or sanding papers for performing sanding, theevaluation is often not reproducible and in consistent. The weight lossdata generated by this method provide a quantitative measure forsandability evaluation.

It is preferred that the coating is sanded under a controlled sandingcondition, such as using a certain sanding block, with a certain numberof sanding strokes, with certain sanding force applied to the sandingforce regulator, and with given sanding directions. Weight loss data onone or more coatings produced after sanding under the controlled sandingconditions can be directly associated to sandability of the coatings.Sandability of one or more coatings can be compared using weight lossdata. For example, two coatings can be sanded under same pre-determinedconditions, one coating having greater weight loss can be assigned “easyto sand” sandability, while the other coating having less weight losscan be assigned a sandability “hard to sand”. Those skilled in the artcan also use other descriptive terms, such as numerical or alphanumerical characters to describe sandability. One commonly useddescriptive is numerical rating, such as a 1-10 rating with 1 being mostdifficult to sand and 10 being easiest to sand.

Method of this invention can be used for measuring and comparingsandability of various coatings. A coating can be a single layer formedby a single coating composition, such as a primer. A coating can also beof multiple layers, such as a finished automobile body that typicallyhas at least one layer of primer, one or more layers of basecoat withpigments that produce colors, and one or more layers of clearcoat thatproduce desired gloss and other desired coating properties.

Sanding is usually performed to remove certain defects of a coating,such as slight variations on thickness, dripping marks, or brush strokemarks. Sanding also creates a rough surface to provide adhesion for nextlayer of coating. For example, a primer layer is usually sanded to evensurface with certain roughness so a basecoat can be applied.

In other situations, sanded surface need to be polished by a processknown as buffing to achieve desired smoothness, for example, clearcoatused for high gloss of an automobile finish. A buffing step can be usedto polish the sanded coating. Buffing can also be done independentlywithout prior sanding.

This invention is also directed to a method for measuring buffability ofa coating. In one embodiment, the method of this invention comprises thefollowing steps.

In step e) (15), initial surface characteristics of the coating can bemeasured using a surface measuring device. Surface characteristics ofthe coating surface can also be measured using a variety of othermethods, for example, by visual examination by naked eyes or usingoptical microscope. It is preferred in this invention that the coatingsurface is measured using surface measurement devices. Aforementioneddevices such as gloss meter, imaging device, profilometer, or acombination thereof, can be suitable for this invention.

In step f) (16), the coating can be buffed using a buffing device tocreate a buffed coating surface. A number of commercial buffing devisesare available. For example, orbital high speed polisher available fromDeWalt Hampstead, Md. 21074, can be suitable for this invention. Buffingcan be done manually or automatically with electronic controls.

One example of a buffing device with automatic electronic control isshown in FIG. 3. A buffing head assembly (301) can comprise a buffinghead (306) coupled to a power source (303) such as a DeWalt high speedpolisher. The buffing head and the power source are the attached to abuffing arm (302) though one or more buffing couplings (305). Thebuffing arm can be affixed to the frame (204) though a frame coupling(304). A buffing pad or other buffing medium can be attached to thebuffing head (306). A coating substrate (307) can be held by a buffingholder (308). An electronic controller can control buffing speed andbuffing time. Such buffing controller is well known to those skilled inthe art. A buffing pressure can also be applied through the buffing armto the buffing head to modulate contact pressure between the buffinghead and the substrate.

In step g) (17), surface characteristics of the coating after buffingcan be measured using the surface measuring device. It is understoodthat corresponding measurement should be used, for example, if theinitial characteristics comprise gloss meter measurement, the subsequentcharacteristics should also comprise gloss meter measurement. It is alsopreferred that the same surface measurement device is to be used formeasuring the initial and the subsequent characteristics.

Surface characteristics that can be measured by an imaging deviceinclude, but not limited to, microstructures, such as microscopic linesor dents cutting into a coating surface, or dots or small areasprotruding from the coating surface that contribute to roughness of thecoating surface. Images of a coating surface before and after buffingcan be captured using the imaging device and the images can be enlargedto show those microscopic lines, dents or other surface characteristics.Such microscopic lines or dents can be counted manually or automaticallyusing a computer implemented method. Image analysis data, such as thenumber of lines or dents in a given area or linear length can begenerated and compared for the coating surface before and after buffing.Buffability data that represent how easy the coating can be buffed toreduce roughness of the coating surface can be generated based on theimage analysis data. Buffability of a plurality of coatings can becompared.

Another method to measure surface characteristics is to measure gloss ofthe surface. A sanded surface reflects lights in less unidirectionalfashion due to roughness of the surface. Buffing generally reducesroughness and therefore increases unidirectional light reflection thatcan be measured with a gloss meter. Gloss meters available fromByk-Gardner, Columbia, Md. 21046, are suitable for this invention.

Yet another method to measure surface characteristics is to useproliformeter. A proliformeter measures not only the number of abovementioned lines, dots, or dents, but also measures depth of those lines,dots, or dents. Buffing can reduce the number of those lines. Under somesituations, some of the lines are not completely buffed away, butreduced in depth. Profilometer is suitable for measuring such reductionin both the number and depth of the lines.

Buffability of a coating describes how easy to reduce surface roughnessof the coating. Buffability can be determined with buffability data thatcan comprise parameters, such as buffing time, roughness of the coatingsurface, types of buffing pads, buffing rotor speeds, or buffingpressures. Roughness of the coating surface can be described by thenumber of lines per millimeter; gloss meter reading; or proliformetermeasurement, such as depth or height of the microstructures, or thenumber of microstructures in a certain area. If conventional buffingmedia is used, the type of buffing media can also be part of thepre-determined constant conditions. Buffability of a plurality ofcoatings can be compared based on the buffability data.

In one example, some of the parameters, herein referred to as constantparameters, such as type of buffing pads, buffing rotor speed, orbuffing pressure, can be kept constant. Other parameters, hereinreferred to as varying parameters, such as buffing time needed forreaching a certain gloss meter reading, can be used to comparebuffability of a plurality of coatings.

In another example, buffing conditions, such as buffing time, buffingpad and buffing rotor speed, are kept constant when buffing a pluralityof coatings individually. Profilometer measurements of each of theindividual buffed coatings, such as height of microstructures or thenumber of microstructures per millimeter, can be used to comparebuffability of the plurality of the coatings.

This invention is also directed to a system for measuring sandability ofa coating. In one embodiment, said system comprises a sanding device anda weight measuring device. The sanding device further comprises asanding head assembly; a substrate holder that holds a substrate coatedwith said coating; and a movement control device that causes relativemovement between the substrate holder and the sanding head assembly. Thesanding head assembly can further comprise a sanding force regulator formodulating force applied to the sanding head.

The weight measuring device can be a balance capable of measuring weightdifferences in a range of from 0.0001 gram to 1 gram.

The system of this invention can further comprise a buffing device and asurface measuring device.

Although a coating is specifically described, the method of thisinvention can also be use for measuring sandability or buffability ofother articles, surfaces, or a combination thereof. For example,sandability of certain material, such as metal, plastic, or wood, can bemeasured by sanding samples of those materials and obtaining weight lossdata. Buffability of those materials can be measured by sanding, buffingand measuring surface characteristics of samples of those materials.

EXAMPLES

The present invention is further defined in the following Examples. Itshould be understood that these Examples, while indicating preferredembodiments of the invention, are given by way of illustration only.From the above discussion and these Examples, one skilled in the art canascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various uses andconditions.

Example 1 Sanding of Coatings

Four different primers were coated onto metal testing panels usingconventional spray application methods. Each primer was coated onto atleast 4 separate testing panels. The four primers were 3240S, 1107S1140S and 131S available from DuPont, Wilmington, Del. The coatedprimers were cured for 23-25 hours at room temperature.

Each of the 4 testing panels for each primer was sanded for 16 strokesby one of the four independent operators using the sanding device shownin FIG. 2. Sanding was done in X-X′ directions.

Initial weights of each of the testing panels were obtained by weighingusing a balance. After the 16 stroke sanding, subsequent weights wereobtained using the same balance. Weight loss for each of the testingpanels after sanding was calculated as sandability data and shown inFIG. 4.

Based on the sandability data, Primer 1 (3240S) had smallest weight lossunder the given sanding conditions and was the most difficult to besanded among the four primers tested. Primer 4 (131S) had the greatestweight loss and was the easiest among the 4 primers tested. Numericalvalues can also be associated to the primers to indicate individualsandability, such as “3” for primer 1, “5” for primer 2 (1107S), “6” forprimer 3 (1140S) and “8” for primer 4.

Example 2 Buffing of Coatings

A testing panel coated with a clearcoat 7600S, available from DuPont,Wilmington, Del., was sanded for 8 cycles using the sanding device shownin FIG. 2. The panel was then buffed using 2000 RPM buffing rotor speed,with buffing compound Perfect-It III, available from 3M, St. Paul, Minn.55144. Buffing time was selected between 6 seconds to 120 seconds.

Profilometer measurements are shown in FIG. 5. The profilometer used wasnano-scratch tester from CSM Instruments Inc. (Needham, Mass., USA). Theprofilometer measured heights of microstructures, shown as “impact” datain FIG. 5, on the clearcoat surface that were mostly microscopic linescaused by sanding and also the number of lines per millimeter, shown as“frequency” data in FIG. 5. Buffing is mostly effective in reducingheights of microstructures at high frequency. FIG. 5A shows profilometermeasurement of the clearcoat after sanding, but before buffing. After 6seconds buffing (FIG. 5B), most of high frequency microstructures werereduced in heights. After 48 second buffing (FIG. 5C), a furtherreduction in heights were achieved.

Example 3 Comparing Buffability of Coatings

Two clearcoats are sanded and buffed under same sanding and buffingconditions as described in Example 2. Profilometer measurements areobtained for both clearcoats. Both clearcoats have similar “impact” dataindicating similar height and frequency of surface microstructuresbefore buffing. After 6 second buffing, a first of the two clearcoatshows more than 80% reduction in heights while a second of the twoclearcoat only has about 20% reduction in heights.

It is concluded that the first clearcoat has a buffability as “easy tobuff” while the second clearcoat is more difficult to buff.

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 5. (canceled) 6.A method for measuring buffability of a coating comprising the steps of:e) measuring initial surface characteristics of the coating using asurface measuring device f) buffing the coating to create a buffedcoating surface; and g) measuring subsequent surface characteristics ofthe buffed coating surface using the surface measuring device.
 7. Themethod of claim 6, wherein the surface measuring device is selected froman imaging device, a gloss meter, a profilometer, or a combinationthereof.
 8. A method for comparing sandability of a plurality ofcoatings, said method comprising the steps of: a) measuring individualinitial characteristics of individual substrates each coated with one ofsaid plurality of coatings; b) sanding the coating on each of theindividual substrates; c) measuring subsequent characteristics of eachof the individual substrates after the step c); and d) obtainingindividual differences between the individual initial and thecorresponding subsequent characteristics.
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 31. A method for comparing buffability ofa plurality of coatings comprising the steps of: e) measuring initialsurface characteristics of each of the coatings using a surfacemeasuring device; f) buffing each of the coatings to create individualbuffed coating surfaces; and g) measuring a subsequent surfacecharacteristics of the buffed coating surfaces using the surfacemeasuring device.
 32. The method of claim 31, wherein the surfacemeasuring device is selected from an imaging device, a gloss meter, aprofilometer, or a combination thereof.
 33. The method of claim 31further comprising the steps of generating buffability data based on theinitial surface characteristics and the subsequent surfacecharacteristics and comparing buffability of the plurality of coatingsbased on the buffability data.
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 40. (canceled)41. A method for measuring buffability of an article comprising thesteps of: a. measuring initial surface characteristics of the articleusing a surface measuring device; b. buffing the article create a buffedsurface; and c. measuring subsequent surface characteristics of thebuffed coating surfaces using the surface measuring device.
 42. Themethod of claim 41, wherein the surface measuring device is selectedfrom an imaging device, a gloss meter, a profilometer, or a combinationthereof.